Conventionally, there is known a power saving technology for display devices such as televisions and displays, by detecting a condition that the user has not been using the display and by shutting down a display.
For example, the power saving is achieved by turning off the television in accordance with a detection state of a user's face captured by a capturing module, thereby preventing the television from displaying images while there are no viewers around.
Further, there is disclosed a technology of detecting a user who is not seated on a predetermined seat by capturing its image with a camera, thereby stopping to display images on the display screen.
When only one camera device is used to perform detection of user presence and user authentication, and when the display is turned on or off in accordance with the user presence, it might be considered to provide a screen lock function which works in association with turning on and off of the display, in order to improve security.
However, if the user presence detection process and the user authentication process are performed independently, because access to the camera is exclusive, contention might occur in use of the camera device, and might result in a deadlock depending on some conditions.